Vibronic and rovibrational spectroscopy of molecules and molecular clusters in helium nanodroplets | Posted on:2006-12-29 | Degree:Ph.D | Type:Thesis | University:University of Southern California | Candidate:Slipchenko, Mikhail N | Full Text:PDF | GTID:2451390008458560 | Subject:Physical chemistry | Abstract/Summary: | | This thesis covers a divergent list of topics, which include the development of new experimental methods and state of the art experiments in the field of He droplet matrix isolation technique.;The first generation of a pulsed (30-100 mus) beam of helium droplets ( = 104-105) is reported and the performance of the beam source is characterized.;LIF excitation spectra of free base phthalocyanine (Pc), Mg-Pc and Zn-Pc molecules in superfluid helium droplets have been studied. The phonon wings reveal discrete structures suggesting localization of some helium atoms in the neighborhood of the molecules.;Pulsed infrared (nu ≈ 2350 cm-1) laser excitation spectra of CO2 molecules embedded in helium droplets are reported. The observed satellite band in the vicinity of the R(0) rovibrational line is assigned to a simultaneous rovibrational excitation of the molecule and its helium solvation shell.;Depletion spectra of the nu1, nu3, and 2nu 4 vibrational bands (nu = 3000-3500 cm-1) of ammonia molecules embedded in He droplets have been studied. The effective rotational constants of ammonia in helium, BHe and CHe, and the magnitude of the inversion splitting are found to be within 5% of that of the free molecule.;Clusters of methane molecules (CH4)n, having n = 1 ∼ 104 have been studied by IR depletion spectroscopy of the nu3 band in He droplets. The spectra of the clusters having n = 1 ∼ 640 demonstrate rotational structure.;A new method of measuring integral intensities of molecular clusters is reported. An increase of the integral intensity by about 4 times per hydrogen bond in (NH3)n (n=2-4) clusters compared to the monomer integral intensity is observed in the 3mum region.;Clusters of ammonia molecules (NH3)n, having n = 2 ∼ 103 have been studied by IR depletion spectroscopy of the nu1, nu3, and 2nu 4 bands in He droplets. With increase of the cluster size to about n ≈ 100 the vibrational shift saturates and the spectrum shape becomes similar to that of amorphous phase of solid ammonia. | Keywords/Search Tags: | Molecules, Helium, Clusters, Droplets, Rovibrational, Spectroscopy, Ammonia | | Related items |
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